Instrument sterilization container system

ABSTRACT

A sterilization container system for sterilizing instruments provides at least two sterilization enclosures separated vertically by a stacking device. The stacking device allows diffusion between the enclosures and into the enclosures through their upper and lower facing portions.

This is a continuation of prior application Ser. No. 10/114,212 filedApr. 2, 2002, which is a continuation of prior application Ser. No.08/672,802 filed Jun. 28 1996, now U.S. Pat. No. 6,379,631.

BACKGROUND

1. Field of the Invention

This invention relates to a sterilization container for use insterilizing, storing and transporting and presenting instruments, inparticular medical instruments.

2. Background of the Invention

Most, reusable medical instruments require sterilization before eachuse. Many methods are employed for sterilization, but the most prevalentmethods include: steam autoclaving, vapor phase chemical sterilizationand vapor phase chemical sterilization in combination with a plasmafield. The chemical sterilants include hydrogen peroxide and ethyleneoxide. One of the most versatile, quickest and most effective methodsemploys an initial period of vapor phase hydrogen peroxide followed byapplication of an electromagnetic field which drives the hydrogenperoxide vapor into the plasma state of matter. The plasma phaseenhances the sterilization and when the electromagnetic field isreleased the plasma free radicals recombine to form water and oxygen.

Typically, instruments are placed into a container and then thecontainer is placed into the sterilization device. Portals for thepassage of sterilizing media must be provided. Also, the container isusually provided with a filter material which allows passage of thesterilizing media through the portals and container yet prevents theingress of microorganisms. The portal and filter material may becombined as in the Nichols U.S. Pat. No. 4,704,254, issued Nov. 3, 1987and incorporated herein by reference, or the container may be providedwith a plurality of apertures and then be wrapped prior to eachsterilization in a filter wrapping material such as SPUNGUARD brand CSRwrap available from Kimberly Clark Corporation which is aspunbonded/meltblown/spunbonded (SMS) laminate consisting of nonwovenouter layers of spun-bonded polyolefins and an interior barrier layer ofmelt-blown polyolefins.

Usually, holding devices of one form or another hold one or moreindividual instruments within the container. The holding device maycomprise clips or other such arrangements, which may or may not bespecially adapted to hold a particular medical instrument. One popularholding device simply comprises a plurality of upwardly extendingflexible projections, sometimes called fingers, which prevent theinstruments from moving about within the container and provide minimalcontact with the instruments. Typically, these are provided on a matwhich lies in the bottom of the container.

The ideal sterilization tray or container is compatible with all majorsterilization methodologies, minimizes or eliminates condensationcollection through thin, yet strong, walls, has a long life, is easy tooperate and can be provided for a reasonable cost. Containers presentlyknown suffer from shortcomings which limit their performance in one ormore of these areas. For instance, many trays designed for steamautoclaves are formed of stainless steel which may interfere withformation of a plasma in some systems. Other trays made of polymers maynot have sufficient heat resistance to withstand repeated steamsterilization cycles. Some tray materials interact with chemicalsterilants, and may even decompose the sterilant. Other materials mayabsorb excessive amounts of chemical sterilants, thereby decreasing thesterilization effectiveness by decreasing the amount of sterilantavailable for sterilizing.

SUMMARY OF THE INVENTION

A sterilization container system for sterilizing instruments accordingto the present invention allows multiple sterilization enclosures to bestacked vertically during a sterilization procedure while maintainingadequate diffusion of sterilant into the enclosures. The systemcomprises a first enclosure having a bottom surface and an upstandingsidewall therefrom and a second enclosure having a bottom surface and anupstanding sidewall therefrom. A stacking device fits between the firstenclosure and the second enclosure, the first enclosure being disposedabove the second enclosure. The stacking device comprises one or morespacers between the first enclosure and the second enclosure to elevatethe first enclosure above the second enclosure and side membersconnected to the one or more spacers and disposed lateral of the firstenclosure and second enclosure whereby to inhibit lateral movement ofthe first enclosure with respect to the second enclosure thus providinga flow path through the stacking device and between the first enclosureand the second enclosure.

Preferably, an interior of the second enclosure is in fluidcommunication with an environment surrounding through the flow paththrough the stacking device. For instance, the second enclosure cancomprise a top surface connected to the first enclosure upstandingsidewall, this top surface having one or more diffusion aperturestherethrough. The first enclosure bottom surface preferably comprisesone or more diffusion apertures therethrough. Preferably, the sidemembers comprise a wall having an elongated lateral opening. Preferably,the elongated lateral openings have a height which matches the spacingbetween the first enclosure and the second enclosure. In one preferredembodiment, the stacking device has a rectangular shape with one of thespacers in each corner.

Preferably, the first enclosure, the second enclosure and the stackingdevice are formed of a thermoplastic liquid crystal polymer and resistchemical attack from hydrogen peroxide, and ethylene oxide, resistabsorption by hydrogen peroxide, do not unduly interfere with anyelectromagnetic fields, and resist attack from elevated temperatures ofsteam sterilization. The thermoplastic liquid crystal polymer preferablycomprises a wholly aromatic polyester. Suitable examples include:polybenzoate-naphthalate;polybenzoate-terephalate-bisphenol-isophthalate;polybenzoate-terephalate-ethylene glycol; and polynapthalate-aminoterephthalate.

The container system can comprises more than two enclosures and morethan one stacking device. In one preferred embodiment, the stackingdevice comprises outwardly facing ribs on the side members whereby tostiffen the stacking device and separate it horizontally from an anotheradjacent stacking device. Each of the enclosures can further includesmeans for holding a medical instrument against movement within thecontainer. Preferably, ingress to each of the enclosures is filteredthrough a filter permeable to sterilizing vapors and impermeable tocontaminating microorganisms, such as by the filter being wrapped abouteach of the enclosures.

A method of sterilizing instruments according to the present inventioncomprising the steps of: placing one or more of the instruments into afirst enclosure; placing one or more of the instruments into a secondenclosure; stacking the first enclosure atop the second enclosure with astacking device between the first enclosure and the second enclosure,the stacking device vertically separating the first enclosure and thesecond enclosure and restraining horizontal movement of the firstenclosure with respect to the second enclosure; and diffusing asterilant between the first enclosure and the second enclosure and intothe second enclosure through an upper portion thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, perspective view of a sterilization containeraccording to the invention;

FIG. 2 is a perspective view of the assembled sterilization container ofFIG. 1;

FIG. 3 is a perspective view of the inverted lid of the sterilizationcontainer of FIG. 1;

FIG. 4 is a cross-section taken along lines 4—4 of FIG. 2;

FIG. 5 is a perspective, disassembly view of a portion of asterilization container according to the present invention whichillustrates an alternative latching mechanism according to the presentinvention;

FIG. 6 is a cross-section of the latching mechanism of FIG. 5, with thelatch shown in the closed position;

FIG. 7 is a perspective view of a further embodiment of a sterilizationtray according to the present invention;

FIG. 8 is a cross-section taken along line 8—8 of FIG. 7;

FIG. 9 is a perspective view of a stacking device according to thepresent invention;

FIG. 10 is a side view of the stacking device of FIG. 9 positionedbetween two sterilization containers to stack and separate thecontainers;

FIG. 11 is a perspective view of a further embodiment of a stackingdevice according to the present invention; and

FIG. 12 is underside plan view of a further embodiment of a lidaccording to the present invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a first embodiment of a sterilization container 10according to the present invention. The container 10 comprises a tray12, a mat 14, and a lid 16. The tray 12 comprises a rectangular base 18from which extends upwardly two opposing side walls 20 and two opposingend walls 22. Corners 24 formed between the side walls 20 and end walls22 are rounded for a pleasing appearance, improved strength, and toreduce sharp edges which may compromise the integrity of an operator'sprotective rubber glove (not shown). A fillet 26 between the base 18 andthe side and end walls 20 and 22 also enhances the strength of the tray12.

The base 18 comprises a plurality of drainage wells 28, each onecomprising a downwardly sloping surface 30 terminating in a drainageaperture 32. The sloping surfaces 30 of adjacent drainage wells 28intersect to form peaks 34. Preferably, the peaks 34 form distinct linesor singularities, as opposed to rounded interfaces between adjacentsloping surfaces 30. This minimizes the surface areas of the peaks 34which support the mat 14, thereby reducing the area of contact betweenthe base 18 and mat 14. Thus, little space is provided in whichcondensate or other liquid matter may become trapped.

The mat 14 has a plurality of mat apertures 38 therethrough and aplurality of upwardly extending projections 36 for holding medicalinstruments (not shown) that are to be sterilized within the container10. Apertures 38 on the mat 14 align with drainage apertures 32 throughthe tray base 18. Preferably, the mat 14 is formed of a silicone orother elastomeric substance which resists high heat associated withsteam autoclaving, and also resists chemical attack from hydrogenperoxide, ethylene oxide, or other chemical sterilants or theirprecursors, particularly the oxidizing type sterilants. Further, thematerial of the mat 14 should not absorb or chemically interact withsuch chemical sterilants.

The upwardly extending projections 36 may take several forms. Forinstance, they may taper upwardly, or have constant diameter. The tipmay be flat, rounded or radiused. They may be relatively soft or theymay be rigid. The total number and spacing of the projections 36 mayalso be varied. Such mats are known in the art, and it is well withinthe ordinary skill of a practitioner in the art to vary these designparameters to achieve a desired overall effect.

The container lid 16 has a plurality of lid apertures 40 to promote thepassage of sterilizing vapors therethrough. The lid apertures 40 mayalign with the drainage apertures in the tray 12, but need not be soaligned. The lid 16 further comprises downwardly depending sidewalls 42and endwalls 44.

Turning also now to FIG. 2, the tray 12 and lid 16 are sized so that thetray endwalls or sidewalls and endwalls 20 and 22 fit snugly within thelid sidewalls and endwalls 42 and 44. Preferably, a latching mechanism46 is integrally formed in the tray 12 and lid 16. Each of the baseendwalls 22 has a recessed portion 48. A pair of U-shaped cutouts 50 ineach recess portion 48 define a flexible tang 52. An upper extent 54 ofeach tang 52 comprises a sloped camming surface 56 and a retaining lip58. Recessed portions 60 in the lid 16 align with the endwall recesses48 and comprise an aperture 62 and retaining lip 64. To engage the latchmechanism 46, the camming surface 56 on each tang 52 is inserted intothe corresponding aperture 62 in the lid 16 and cammed over theretaining lip 64 until the retaining lip 58 on the tang 52 snaps intoengagement with the retaining lip 64. Inward pressure on the tang 52,applied manually, disengages the retaining lips 58 and 64 to release thelatch mechanism 46.

To enhance the flow of sterilizing gases through the container 10, eachof the tray sidewalls 20 and lid sidewalls 42 contain several shallowcutout portions 66. As best seen in FIG. 2, when the lid 16 and tray 12are interconnected, the cutout portions 66 thereon align with each otherto form shallow slit-like openings 68 into the container 10. Thisenhances the flow of sterilizing gases through the container 10.

Turning to FIG. 3, four pads 70 are provided inside of the lid 16 tospace the lid 16 from the tray 12 and thereby minimize any surfacecontact area therebetween which might block the flow of gas or liquid orwhich might trap, condensate, or other liquid material.

FIG. 4 illustrates the drainage enhancing features of the presentinvention. The peaks 34 of the base 18 support the flexible mat 14.Condensate or other liquid which enters between the mat 14 and base 18comes within one of the drainage wells 28. The small contact surface 71formed between the peaks 34 and mat 14 prevents condensate or otherliquids from being trapped between surfaces of the base 18 and mat 14.The downwardly sloping surfaces 30 of the drainage wells 28 encourageany condensate or other liquids to move toward the drainage apertures32. Condensate then physically drains out of the container 10. Thesupporting characteristics of the peaks 34 can not be over emphasized.Silicone and other elastomeric materials suitable for forming the mat 14tend to soften considerably in high temperature sterilizingenvironments. Accordingly, it is crucial to properly support the mat 14.

The selection of tray material for use in hydrogen peroxide or chemicalbased sterilization technology is influenced by the chemical resistanceand inertness of the material with respect to the sterilant or precursorfor chemical plasma. For chemical plasma sterilization methods whichdepend on excited free radicals, the inertness of the material withrespect to the plasma precursor is even more critical due to possiblelow concentrations of precursor available to generate plasma in somepreferred plasma methodologies. The tray material should be non-reactiveto the sterilant(s), or the precursor(s) for the chemical plasma inorder not to affect biological lethality of the sterilizer chamber. Forease of operation, the material should also be resistant to the chemicaland thermal environments during the cleaning and decontaminationprocedure of instruments and trays as commonly used in clinicalsituations. Hospitals typically use a washer/decontaminator operating at270° F. as well as detergents and enzymatic cleaners for removingorganic matter.

The ideal tray material should further be compatible with all majorsterilization methods employed by hospitals and the like, includingsteam (flash and gravity), ethylene oxide gas, and hydrogen peroxidebased sterilizers. One example of the hydrogen peroxide based plasmasterilization is the STERRAD Sterilization System that uses hydrogenperoxide plasma to eliminate microorganisms on medical instruments.Therefore, the ideal material should have adequate thermo-mechanicalproperties to withstand steam, exhibit low ethylene oxide residualsafter processing, and have extremely low interaction with H₂O₂ or otheroxidative sterilants.

We have rigorously examined and tested many materials to identify amaterial suitable for such varied and extreme service environments. As aresult of our investigations, we have found the preferred materials tobe neat (non-reinforced) and reinforced polyester based liquid crystalpolymers, neat and reinforced polyesters, and reinforced polypropylene.The most preferred material is neat or reinforced polyester liquidcrystal polymer, or its blend with the above mentioned polymers. Onecommercially available example of a suitable liquid crystal polymer isthe Vectra® family produced by the Hoechst Celanese Corporation.

Within each family group, there are preferred chemical structures,either with or without reinforcement, which can be considered as traymaterials:

I. Reinforced polypropylene, especially when reinforced with calciumcarbonate or glass fiber, provides the chemical inertness and structuralproperties required for multi-sterilization application.

II. Polyester type polymers have a variety of basic structures, amongthem:

1. Polyethylene terephthalate (PET) with the following chemicalstructure:

2. Polybutylene terephthalate (PBT), in which chemical structure is:

and

3. Polycyclohexylene terephthalate (PCT), with the following chemicalstructure:

PCT is available from Eastman Chemical Company under the tradename of“Ektar”, in a variety of unmodified and modified structures.Modification may include acids and glycol structures.

Among the polyester family, the structure of polyethylene terephthalateis preferred. The most preferred configuration is glass fiber reinforcedPET. The fiber reinforcement provides structural strength for steamautoclave operation and is preferred in oxidative chemical vapor oroxidative chemical plasma sterilization methods.

III. Liquid crystal polymers, in which there are four major structuralvariations:

1. Polybenzoate-naphthlate

An example of a commercially available product is under the tradenameVECTRA®A and C series by Hoechst Celanese Corporation.

2. Polybenzoate-terephthalate-bis phenol-isophthalate

An example of a commercially available product is under the tradename ofXydar® by Amoco Performance Products.

3. Polybenzonate-terephthalate-ethylene glycol

An example of a commercially available product is under the tradename ofX7G and X7H by Eastman Chemical Company and

4. Polynaphthalate-amino terephthalate

An example of a commercially available product is under the tradename ofVectra®B series by Hoechst Celanese Corporation.

The most preferred structures are the wholly polyester aromatic liquidcrystal polymers, which are polybenzoate-naphthalate andpolybenzoate-terephthalate-bis phenol-isophthalate. Both neat andreinforced grades are preferred due to the structural strength of thismaterial family. The most preferred reinforcements fillers are glass ormineral fibers, or fluoropolymers in powders.

The material characteristics in a hydrogen peroxide environment are ofparticular importance. Both the tendency to absorb hydrogen peroxide andthe tendency to decompose hydrogen peroxide were studied for a varietyof materials. The following Table 1 illustrates the results for some ofthe more important materials.

TABLE 1 H₂O₂ H₂O₂ Material Material Absorption Decomposition TradenameFamily (ppm) (g/g) Ultem 1000 Polyetherimide 144.3 Ultem CRS 5011Polyetherimide 346 Radel R-5100 Polyaryl sulfone 356 Noryl Polyphenylene52 oxide/Polystyrene blend Vectra A530 Polyester liquid 4.5 0.009crystal polymer (mineral fiber filled) Vectra A115 Polyester liquid noabsorption 0.013 crystal polymer (glass fiber filled) DPP40W18357 40%calcium no absorption 0.012 carbonate filled polypropylene Ektar EG-015Glass fiber filled 3.3 no poly ethylene decomposition terephthalate

Another study was conducted to evaluate the compatibility of traymaterials with simulated hydrogen peroxide plasma sterilization andwasher/decontamination cycles, which includes alternating hydrogenperoxide plasma sterilization cycle, washer/decontaminator cycle andenzymatic cleaner immersion. The samples were placed under 0.5% and0.75% strain. The following Table 2 illustrates the results of thisevaluation.

TABLE 2 Strain Yield Tensile Elongation at Material Level StrengthStrength Break Ultem 1000 Control 15,320 psi 14,690 psi 68.5% Ultem 10000.5% 10,140 psi 10,140 psi 2.4% (a) Ultem 1000 0.75% 11,630 psi 11,230psi 4.2% (a) Noryl Control 9,965 psi 7,852 psi 13.1% Noryl 0.5% 10,400psi 7,961 psi 9.3% Noryl 0.75% 10,550 psi 8,091 psi 98.5% Vectra A530Control n/a 22,672 psi n/a Vectra A530 0.5% n/a 22,371 psi n/a VectraA530 0.75% n/a 22,431 psi n/a Vectra A115 Control n/a 24,265 psi n/aVectra A115 0.5% n/a 23,266 psi n/a Vectra A115 0.75% n/a 23,485 psi n/aDPP40WI Control 3,258 psi 2,699 psi 19.27% DPP40WI 0.5% 2,862 psi 2,449psi 54.42%

Aside from using chemically inert material, there are other controllingcharacteristics of sterilization trays or containers so as to reduceinteraction with the sterilization environment and so as to enhance theresistance to hospital-use cleaning chemicals. Interaction of traymaterial with the sterilants or precursor for chemical plasma reducesthe available sterilant or precursor for chemical plasma in vapor phaseso as to effect the biological lethality. Resistance to hospital-usechemicals will lengthen the expected product life. The firstcharacteristic to be controlled is the surface smoothness of finalproduct. The surface of the sterilization tray should be as smooth aspossible so as to reduce surface area/volume ratio. Since both chemicaland physical interactions with sterilants or precursor(s) for chemicalplasma and material degradation are a function of the surfacearea/volume ratio, smooth surfaces will reduce the rate of theseinteractions.

The second characteristic to be controlled is wall thickness. Wallthickness is integral to the structural strength of the tray orcontainer. For the sterilization tray or container to operate in anoxidative chemical vapor or chemical plasma environment, often underreduced pressure and low concentration, the condensation of chemicalsterilant or precursor for chemical plasma should be minimized.Condensation is a function of the thermal mass and heat transfercharacteristics of the tray or container, which may reduce the amount ofavailable sterilant or precursor for chemical plasma in vapor phase andthereby effect the biological lethality. To minimize the thermal massand enhance the heat transfer characteristics, the wall thickness of thetray or container should be minimized.

Accordingly, the preferred materials for forming the tray 12 and lid 16are as follows:

I. Reinforced polypropylene: Reinforced polypropylene, especially whenreinforced with calcium carbonate or glass fiber, will provide thethermo-mechanical structural integrity required for multi-sterilizationapplication.

II. Neat or reinforced polyester: Among the polyester family, thestructure of polyethylene terephthalate is preferred. The most preferredconfiguration is glass reinforced polyethylene terephthalate (PET). Thefiber reinforcement provides structural strength for steam autoclaveoperation and allows for a thin-wall design, which is preferred inoxidative chemical vapor sterilization method.

III. Neat or reinforced liquid crystal polymer, and/or a blend of theabove materials. The most preferred structures are the wholly polyesteraromatic liquid crystal polymer, which can be of the chemical structureof polybenzoate-naphthalate or polybenzoate-terephthalate-bisphenol-isophthalate. Both neat and reinforced grades are preferred dueto the thermo-mechanical strength of this material family. The mostpreferred reinforcements types are glass and mineral fibers.

IV. A blend or alloy of liquid crystal polymers and I or II of theabove.

FIGS. 5 and 6 illustrate a second embodiment of a sterilizationcontainer according to the invention. The container 72 comprises a tray74, lid 76 and mat (not shown) similar to the previous embodiment.However, it incorporate an alternative latching mechanism 78.

The lid 76 comprises an apertured top wall 80; side and endwalls 82 and84, respectively, depending therefrom. A latch member 86 is integrallymolded into a recessed portion 88 in each endwall 84 of the lid 76. Apair of torsion bars 90 extend inwardly of the recess portion 88 fromopposing sidewalls 92 thereof to rotatably support the latch member 86.The torsion bars 90 bias the latch member 86 into a standing, engagedposition as shown best in FIG. 6, and allow a limited amount of rotationaway from the engaged position.

A notch 94 in each endwall 96 of the tray 74 forms an engagement surface98. A lip 100 protruding from a lower portion 102 of the latch member 86engages the engagement surface 98 on the tray 74 to thereby hold the lid76 securely to the tray 74. Finger pressure against an actuation surface104 on an upper portion 106 of the latch member 86 pivots the latchmember 86 about the torsion bars 90 to disengage the engagement surface98 from the lip 100 and thereby release the lid 76 from the tray 74.When the pressure on the actuation surface 104 is release, the torsionbars 90 return the latch member 86 to its standing, engaged position.

All edges and surfaces of the latch member 86 are rounded and smoothespecially those on that portion 108 of the latch member facingoutwardly of the recess 88. The only exception is the lip 100 which lieson that portion 109 of the latch member facing inwardly of the tray 74,to thereby present no sharp edges or surfaces which may engage and tearthe users protective glove (not shown). All portions of the latchingmechanism 78 are integrally molded with either the tray 74 or lid 76thereby reducing manufacturing and assembly costs. Of course, theorientation of the latching mechanism 78 may be reversed, such that thelatch member 86 is formed in the tray 74. Further, the lid 76 could beadapted to pivot about a hinge (not shown) and of course, the latchingmechanism 78 need not be provided in the endwall 84 but could be locatedelsewhere on the container 72. However, the orientation illustrated inFIG. 5 is particularly convenient.

FIGS. 7 and 8 illustrate an alternative arrangement for a tray 110according to the invention. The tray 110 may be used with asterilization container as in the first and second embodiment anddiffers primarily in its base 112. The base 112 comprises a flat panel114 having a plurality of apertures 116 therethrough. Additionally, anumber of larger, elongated apertures 118 penetrate the panel 114 and anupwardly extending lip 120 encircles each of the elongated apertures118. The lips 120 support a mat 122 and further provide rigidity to thetray base 112. Apertures 124 through the mat 122 aligned with theelongated apertures 118 through the tray base 112 to provide anefficient diffusion path for sterilizing gases.

FIG. 9 illustrates a stacking device 124 for stacking sterilizationtrays 10 during a sterilization procedure. The stacking device 124 isrectangular in shape and of slightly larger dimensions and than thesterilization tray 10 (not shown in FIG. 9). It comprises verticalsidewalls 126 and vertical endwalls 128. An L-shaped shelf member 130extends horizontally inwardly from each corner 132 of the stackingdevice 124. As illustrated in FIGS. 9 and 10, each of the sidewalls 126and endwalls 128 has elongated openings 134 therethrough of similarvertical dimensions to the shelf member 130 so that when containers 10are stacked using the stacking device 124, the flow of sterilizing gasesinto and out of the individual containers 10 is not impeded by thestacking device 124.

FIG. 10 shows two sterilization containers 10, each wrapped in a sterilewrap material 136. The stacking member 124 sits atop a first tray 10with the shelf member 130 resting upon the tray 10. The second tray 10rests upon the shelf member 130. Both trays 10 are positioned within theside and endwalls 126 and 128 of the stacking device. Thus, the twotrays 10 are stacked and separated from each other with a full and openflow path thereabout.

FIG. 11 illustrates an alternative embodiment of a stacking device 138.In place of the opening 134, each of the side and endwalls 140 and 142respectively have a low vertical profile vertically offset from a shelfmember 144 to thereby provide an open flow path to the stacked trays(not shown in FIG. 11). Vertical ribs 146 on the side and endwalls 140and 142 provide rigidity and maintain an open flow path, if the stackingdevice is placed next to another stacking device or flat surface.

FIG. 12 illustrates an alternative embodiment of a lid 150 according tothe invention. The lid 150 duplicates the lid 16 of FIGS. 1 and 3, withseveral modifications. Accordingly, features similar to those on the lid16 will be designated with similar numerals with the addition of asingle prime symbol (′). Specifically, the lid 150 differs from the lid16 in its mixture of round and elongated apertures 152 and 154respectively. Also, an additional fillet 156 has been added at eachcorner which both strengthens the lid 150 aids in lifting the lid 150above the base 8 (not shown in FIG. 12) for improved circulation.

Liquid crystal polymers are known for their difficulty in molding. Oneparticular problem arises where opposing flows of molten polymer meet.Such areas often have reduced strength and accordingly it is desirableto locate them away from areas of the molded article which will besubjected to high levels of stress. In the lid 150, the recess 60′ isformed by a core pin in the mold (not shown). The molten polymer flowsaround the core pin and meets to enclose the recess 60′. Normally theseflows would meet at the retaining lip 64′. However, this area issubjected to high stresses. Accordingly, the lid 150 is formed with apair of flow leaders 158, each leading from a center area 160 of the lid150 where the molten polymer is injected in the molding process andleading to an inside corner 162 of the respective recesses 60′. Duringthe molding process the molten polymer thus flows around the core pinand the opposing flows meet at a side portion 164 of the recess 60′.

While the invention has been particularly described in connection withspecific embodiments thereof, it is to be understood that this is by wayof illustration and not of limitation, and that the scope of theappended claims should be construed as broadly as the prior art willpermit.

We claim:
 1. A sterilization container system for sterilizinginstruments, comprising: a first enclosure having a bottom surface andan upstanding sidewall therefrom; a second enclosure having a bottomsurface and an upstanding sidewall therefrom; a stacking device separatefrom and between the first enclosure and the second enclosure, the firstenclosure being disposed above the second enclosure, the stacking devicecomprising: one or more spacers between the first enclosure and thesecond enclosure to elevate the first enclosure above the secondenclosure; side members connected to the one or more spacers anddisposed lateral of the first enclosure and second enclosure whereby toinhibit lateral movement of the first enclosure with respect to thesecond enclosure; and a flow path through the stacking device andbetween the first enclosure and the second enclosure.
 2. A sterilizationcontainer system according to claim 1 wherein an interior of the secondenclosure is in fluid communication with a surrounding environmentthrough the flow path through the stacking device.
 3. A sterilizationcontainer system according to claim 1 and wherein the second enclosurecomprises a top surface connected to the second enclosure upstandingsidewall, this top surface having one or more diffusion aperturestherethrough.
 4. A sterilization container system according to claim 1and wherein the first enclosure bottom surface comprises one or morediffusion apertures therethrough.
 5. A sterilization container systemaccording to claim 1 wherein the side members comprise a wall having anelongated lateral opening.
 6. A sterilization container system forsterilizing instruments, comprising: a first enclosure having a bottomsurface and an upstanding sidewall therefrom; a second enclosure havinga bottom surface and an upstanding sidewall therefrom; a stacking devicebetween the first enclosure and the second enclosure, the firstenclosure being disposed above the second enclosure, the stacking devicecomprising: one or more spacers between the first enclosure and thesecond enclosure to elevate the first enclosure above the secondenclosure; side members connected to the one or more spacers anddisposed lateral of the first enclosure and second enclosure whereby toinhibit lateral movement of the first enclosure with respect to thesecond enclosure; a flow path through the stacking device and betweenthe first enclosure and the second enclosure; and wherein the sidemembers comprise a wall having an elongated lateral opening and theelongated lateral openings have a height which matches the spacingbetween the first enclosure and the second enclosure.
 7. A sterilizationcontainer system according to claim 1 wherein the stacking device has arectangular shape with one of the spacers in each corner.
 8. Asterilization container system according to claim 1 wherein the firstenclosure, the second enclosure and the stacking device are formed of athermoplastic liquid crystal polymer and resist chemical attack fromhydrogen peroxide, and ethylene oxide, resist absorption by hydrogenperoxide, do not unduly interfere with any electromagnetic fields, andresist attack from elevated temperatures of steam sterilization.
 9. Asterilization container according to claim 8 wherein the thermoplasticliquid crystal polymer comprises a wholly aromatic polyester.
 10. Asterilization container according to claim 9 wherein the wholly aromaticpolyester is selected from the group consisting of:polybenzoate-naphthalate;polybenzoate-terephalate-bisphenol-isophthalate;polybenzoate-terephalate-ethylene glycol; and polynapthalate-aminoterephthalate.
 11. A sterilization container system according to claim 1which comprises more than two enclosures and more than one stackingdevice.
 12. A sterilization container system according to claim 1wherein the stacking device comprises outwardly facing ribs on the sidemembers whereby to stiffen the stacking device and separate ithorizontally from an another adjacent stacking device.
 13. Asterilization container system according to claim 1 wherein each of theenclosures further includes means for holding a medical instrumentagainst movement within the container.
 14. A sterilization containersystem according to claim 1 wherein ingress to each of the enclosures isfiltered through a filter permeable to sterilizing vapors andimpermeable to contaminating microorganisms.
 15. A sterilizationcontainer system according to claim 14 wherein the filter is wrappedabout each of the enclosures.
 16. A method of sterilizing instrumentscomprising the steps of: placing one or more of the instruments into afirst enclosure; placing one or more of the instruments into a separatesecond enclosure; stacking the first enclosure atop the second enclosurewith a separate stacking device between the first enclosure and thesecond enclosure, the stacking device vertically separating the firstenclosure and the second enclosure and restraining horizontal movementof the first enclosure with respect to the second enclosure; anddiffusing a sterilant between the first enclosure and the secondenclosure and into the second enclosure through an upper portionthereof.
 17. A method according to claim 16 wherein the second enclosurefurther comprises an upper surface having one or more aperturestherethrough and wherein the step of diffusing the sterilant into thesecond enclosure comprises diffusing the sterilant through the one ormore apertures through the second enclosure upper surface.
 18. A methodaccording to claim 16 wherein the first enclosure further comprises alower surface having one or more apertures therethrough and furthercomprising the step of diffusing the sterilant through the one or moreapertures through the first enclosure lower surface into the firstenclosure.
 19. A method of sterilizing instruments comprising the stepsof: placing one or more of the instruments into a first enclosure;placing one or more of the instruments into a second enclosure; stackingthe first enclosure atop the second enclosure with a stacking devicebetween the first enclosure and the second enclosure, the stackingdevice vertically separating the first enclosure and the secondenclosure and restraining horizontal movement of the first enclosurewith respect to the second enclosure; diffusing a sterilant between thefirst enclosure and the second enclosure and into the second enclosurethrough an upper portion thereof; and wherein the stacking devicecomprises side members laterally outside of the first enclosure andsecond enclosure, the side members comprising a wall having an elongatedlateral opening and the step of diffusing the sterilant between thefirst enclosure and the second enclosure comprises diffusing thesterilant through the elongated lateral openings.
 20. A method accordingto claim 16 wherein the stacking device has a rectangular shape with aspacer in each corner and the step of vertically separating the firstenclosure and the second enclosure comprises interposing the spacersbetween the first enclosure and the second enclosure.
 21. A methodaccording to claim 16 and further comprising placing a second stackingdevice atop the first enclosure and a third enclosure atop the secondstacking device.